A 1-3 micron infrared (IR) circular dichroism (CD) instrument will be extended to 30 microns, allowing for the first time CD and magnetic CD (MCD) measurements in the entire 1-30 micron region. This will involve the development of a photoelastic modulator for phase modulation in the 3-30 micron region. The instrument will be applied primarily to the search for an application of vibrational CD (VCD). VCD has never been observed but recent theoretical work shows that it can be large enough to be observed with currently practicable instrumentation. VCD is expected to be very sensitive to, and an important tool in the study of, molecular stereochemistry. Of especial importance are biological molecules, and models for these--e.g. helical systems.-and these are the focus of applications. Natural and magnetic CD will also be studied in compounds of biological importance where IR electronic transitions exist, primarily iron-containing proteins. Lastly, the instrumentation will permit MCD studies of transition-metal ions in single crystals. These will be directed to the detailed understanding of electronic-vibrational interactions in low-lying excited electronic states and to the study of exchange interactions in simple ion-pairs, of importance in both magnetism and biophysics.